1Department of Endocrinology, University Hospitals Birmingham NHS Foundation Trust, Birmingham, B15 2TH, United Kingdom
2 Experimental and Clinical Endocrinology, MedizinischeKlinik I, RatzeburgerAllee 160, D-23538, Lübeck, Germany
3Department. of Endocrinology, CliniquesUniversitaires Saint-Luc, Avenue Hippocrate, 54.74, 1200 Brussels
4Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden
5Department of Medical Endocrinology, Rigshospitalet, Copenhagen, 2100, Denmark
6KIMS Pfizer Endocrine Care, Specialty Business Unit, Pfizer Health AB, Sollentuna, 190 91, Sweden
7Department of Neurosurgery, University of Erlangen Nuernberg, Erlangen, 91045, Germany
8 Pfizer Endocrine Care Europe, Tadworth, United Kingdom
9Neuroendocrine Unit, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, United States
Objective: To determine whether the ITT, arginine (AST) and glucagon stimulation tests (GST) identify patients who have similar features of GH deficiency using a diagnostic threshold of 3 μg/l.
Patients and Methods: 5453 tests were available from 4,867 patients registered in the KIMS database (49.9% females, ITT = 3111, AST = 1390, GST = 952). Comparisons were made for GH peak, BMI, lipids, waist circumference, waist:hip ratio and quality of life (QoL-AGHDA questionnaire).
Results. There were significant (p<0.0001) intra-individual correlations between the GH peaks for the ITT vs AST (r = 0.655), ITT vs GST (r = 0.445) and AST vs GST (r = 0.632). GH peaks in response to all tests were negatively correlated to the number of additional pituitary hormone deficiencies, and positively correlated to IGF-I SDS. BMI had a negative influence on all three tests.
Comparing GHD patients according to the diagnostic test used, most clinical variables did not differ between the groups. The only exceptions showing any difference were BMI being slightly higher in the AST and GST groups, triglyceride levels increased in the GST group, and IGF-I SDS was lower in the ITT and AST than in the GST group. Waist circumference was larger and quality of life was worse in the GST group than in the other groups.
Conclusions. This study demonstrates that the ITT, AST and GST produce similar GH peaks, are influenced by similar clinical factors and identify patients with similar features of GH deficiency at a diagnostic threshold of 3 μg/L.